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It has been controversial whether Betula tatewakiana, a dwarf birch distributed in Hokkaido of northern Japan, is an endemic species or a synonym of B. ovalifolia broadly distributed in northeast Asia. The endemic hypothesis is based on the idea that B. tatewakiana is diploid while B. ovalifolia is tetraploid and that they are separated based on the ploidy level; however, no chromosome data have actually been published before. Resolving the taxonomic problem is crucial also in judging the conservation priority of B. tatewakiana in a global perspective. Our chromosome observation revealed that B. tatewakiana is tetraploid as well as B. ovalifolia. We also conducted morphological observations and clarified that B. tatewakiana is morphologically identical to B. ovalifolia in white hairs and dense resinous glands respectively on adaxial and abaxial leaf surfaces, in which they differ from closely related species in the same section Fruticosae. We conclude that the hypothesis that B. tatewakiana is a Hokkaido endemic based on the ploidy level is not supported and that B. tatewakiana should be merged with B. ovalifolia.

Shrub encroachment can alter litter decomposition in temperate graminoid-dominated wetlands, yet its influence on the direction of litter mixing effects is still elusive. We collected senesced aboveground tissues of two graminoid species (Deyeuxia angustifolia and Carex schmidtii) and leaf litter of two shrub species (Betula fruticosa and Salix floderusii) in a freshwater marsh of Northeast China, and measured litter mass loss dynamics in monocultures and shrub-graminoid mixtures (in mass ratios of 1:2 and 2:1) using a 730-day incubation experiment. In the monocultures, shrub litter had greater mass loss than graminoid litter presumably due to the relatively higher N, and dissolved organic C and N concentrations. Additive effects were observed in all shrub-graminoid mixtures after 182 days of decomposition, while nonadditive effects gradually became more prominent as litter decomposition proceeded. Salix floderusii leaves usually promoted decomposition of neighboring graminoid litter, especially when S. floderusii dominated, leading to a synergistic effect on mass loss of the whole litter mixtures. However, the effects of B. fruticosa on decomposition of graminoid litter varied with incubation time, species composition and species proportion. At the end of incubation, synergistic effects were observed in B. fruticosa-D. angustifolia mixtures, while additive effects occurred in B. fruticosa-C. schmidtii mixtures. The effects of shrub expansion on the direction of litter mixing effects are dependent on incubation time, shrub species and dominant graminoid types in this freshwater marsh. These findings help to predict the consequence of altered species composition on community-level litter decomposition in temperate graminoid-dominated wetlands.

In addressing the controversial issues of the Late Pleistocene paleogeography of the Caspian basin, an important role is given to the results of the spore-pollen analysis and based on them reconstructions of climate and vegetation changes in the Northern Caspian region during the development of the Early Khvalynian transgression. In this paper we present the main results of the palynological study of deposits (chocolate clays and the overlying and underlying layers from the Srednyaya Akhtuba section) of maximum stage of the Early Khvalynian transgression; the materials are illustrated by pollen diagram with the data of spore-pollen analysis and the detailed list of palynoflora recovered from the studied Lower Khvalynian sequences, and complemented with photographs of pollen belonging to the principal autochtonous taxa and, for comparison, to some redeposited palynomorphs. Palynological materials indicate subaqual (brackish marine and freshwater) sedimentation of the sediments studied in periglacial landscapes and, for the most part, under very harsh climatic conditions. The performed climate-stratigraphic reconstructions do not contradict the data of absolute dating on the accumulation of the studied deposits during the Late Valdai (Ostashkov) late Glacial period. During this interval in the territory of the study area, plant communities of the glacial climate — tundra-steppe, periglacial forest-steppe, periglacial steppe, periglacial parklands and periglacial forests — were developed. The widespread occurrence in the composition of the periglacial vegetation cover of the studied region of the yernik formations from Betula nana and shrub communities from Betula fruticosa, B. nana, Alnaster fruticosus, Juniperus, etc. testifies to the severe climatic conditions and, possibly, the existence of sporadic permafrost in the cold stages (stadials) of the Ostashkov Late Glacial period.

Little is known about the effect of woody plant expansion on decomposition of root mixtures in grass-dominant temperate wetlands. Here, we collected fine roots (

Litter mixing effects during decomposition remain inconclusive for boreal peatlands, and such effects may vary with climate warming and associated shifts in vegetation composition. Here, litters were collected from four common species (deciduous shrub Betula fruticosa, evergreen shrub Ledum palustre, graminoid Eriophorum vaginatum, and moss Sphagnum divinum) in a boreal peatland of northeast China, resulting in 15 species combinations with species richness ranging from one to four. We determined litter mixing effects on carbon (C) mineralization rate and mass loss under aerobic conditions at 10 °C and 20 °C in a 315-d incubation experiment, and assessed the differences in litter mass loss for the individual species within monocultures and mixtures. Non-additive effects on C mineralization and mass loss were prevalent during decomposition of litter mixtures. Moreover, the sensitivity of C mineralization and mass loss to rising incubation temperature (Q10) was found to be non-additive in five and three out of 11 mixtures, respectively. Notably, mass loss of other litters in the mixtures was generally promoted by B. fruticosa, but inhibited by S. divinum in two- and three-species litter mixtures. Furthermore, B. fruticosa increased and S. divinum decreased Q10 values for mass loss of other litters in four out of seven cases. These findings suggest that the shifts in plant community composition will not only influence community-level litter decomposition through altered litter mixing effects during decomposition, but also modulate the response of litter decomposition to rising temperature in boreal peatlands.

Pinus pumila (Dall.) Regel, a rare conifer and key species in high latitude and high altitude mountains, has an important role in soil and water conservation. This evergreen shrub grows 3–6 m high in P. pumila – larch ( Larix gmelini ) open forest at altitudes of 800–1200 m in the Greater Kingan Mountain Range (Daxing’an Mountain). Forest fires are major natural hazards to P. pumila – larch forest. The unique ecological role of this community gives important theoretical and practical significance to research on P. pumila – larch forest restoration after fires. Literature concerning factors influencing early vegetation restoration in burned areas in this habitat is sparse. We studied these factors, especially those related to P. pumila seedling establishment. The results showed fires in P. pumila – larch forest usually resulted in severe burns. Typically almost no P. pumila survived after fires. Nearly all ground fuels were consumed. Second growth after fires exhibited low species richness. The dominant tree/shrub seedlings found after fires were birch ( Betula platyphylla ) and larch, with small number of P. pumila . Other shrub seedlings found were Ledum palustre , Vaccinium vitis-idaea , Betula fruticosa , and Rubus arcticus . The main herb species found were Deyeuxia langsdorffii , and Chamaenerion angustifolium . Important factors influencing early vegetation restoration after fires included seed dispersal, fire size, and site condition. Seed dispersal in birch and larch is higher than in P. pumila ; more seedlings of birch and larch were found in burned areas than seedlings of P. pumila . Most seeds germinated in the first year following a fire. The extent of the burned area influences seedling distribution patterns, especially in species with limited seed dispersal ability. Birch and larch seedlings were evenly distributed in the entire burned area, while seedlings of P. pumila were found only at the fire edge. No P. pumila seedlings were found more than 50 m away from seed source trees. Site condition significantly influenced seed germination and growth in birch and larch; these seedlings only grew well in burned areas with good site conditions (shallow slopes, thick soils, etc.). They did not grow well in burned areas with poor site conditions (steep slopes, thin soils, etc.). However, P. pumila seedlings could grow well in burned areas with either good or poor site conditions. The strong vitality of P. pumila seedlings gives this species an enormous ecological advantage in soil conservation and environmental restoration and conservation. We conclude that the main factor influencing seedling establishment in P. pumila is its weak seed dispersal ability. Although the P. pumila seeds can germinate in all burned areas, natural regeneration rarely restores burned areas to the original P. pumila – larch forest. Planting seeds and/or seedlings may facilitate burned area restoration to P. pumila – larch forest. Because P. pumila seedlings grow very slowly, the restoration process may take decades.

For a sample from the roof of peat (0–2 cm) located in a reference section for the Middle Neopleistocene in West Siberia near the village of Krivosheino, we obtained an exorbitant value of 14C date ≥53.9 ka B.P. (LU-6024). In the peat proper, the 230Th/U dates obtained by the isochronous method are 195.2 ± 10.8/9.1 ka B.P. for the L/L model and 204.1 ± 17/13 ka B.P. for the TSD model. The palynospectra of the peat characterize, from the bottom up, birch forests with fir and spruce participation; then spruce forests with fir; next spruce-cedar forests, similar to the middle taiga subzone. In the clay, the following palynospectra have been examined: forb-gramineous grasslands and light forests with spruce and Betula fruticosa. In the upper part of clays, the palynospectra reflect the evolution of swampy, birch, light forests with spruce participation. The conclusion is made that the studied part of the section formed at the end of the Samarovo Ice Age and in the last third of the Taz Ice Age. The break in sedimentation related to the erosion contact covers a part of the Samarovo Ice Age and the first two-thirds of the Taz Ice Age.

Permafrost records, accessible at outcrops along the coast of Oyogos Yar at the Dmitry Laptev Strait, NE-Siberia, provide unique insights into the environmental history of Western Beringia during the Last Interglacial. The remains of terrestrial and freshwater organisms, including plants, coleopterans, chironomids, cladocerans, ostracods and molluscs, have been preserved in the frozen deposits of a shallow paleo-lake and indicate a boreal climate at the present-day arctic mainland coast during the Last Interglacial. Terrestrial beetle and plant remains suggest the former existence of open forest-tundra with larch (Larix dahurica), tree alder (Alnus incana), birch and alder shrubs (Duschekia fruticosa, Betula fruticosa, Betula divaricata, Betula nana), interspersed with patches of steppe and meadows. Consequently, the tree line was shifted to at least 270 km north of its current position. Aquatic organisms, such as chironomids, cladocerans, ostracods, molluscs and hydrophytes, indicate the formation of a shallow lake as the result of thermokarst processes. Steppe plants and beetles suggest low net precipitation. Littoral pioneer plants and chironomids indicate intense lake level fluctuations due to high evaporation. Many of the organisms are thermophilous, indicating a mean air temperature of the warmest month that was greater than 13 °C, which is above the minimum requirements for tree growth. These temperatures are in contrast to the modern values of less than 4 °C in the study area. The terrestrial and freshwater organism remains were found at a coastal exposure that was only 3.5 m above sea level and in a position where they should have been under sea during the Last Interglacial when the global sea level was 6–10 m higher than the current levels. The results suggest that during the last warm stage, the site was inland, and its modern coastal situation is the result of tectonic subsidence.

Paleopalynological researches of modern sedimentary deposits allowed discovering specifics and tendencies of the development of vegetation cover on the islands of Peter the Great Bay in Holocene under climatic fluctuations and the related with them variations of the sea level as well as under the impact of a human factor. In cold Holocene periods small-leaved-broadleaved forests with Betula fruticosa were widespread. During warm periods broadleaved forests predominated. In the second half of Late Holocene the development of coniferous-broadleaved forests occurred. The climate was colder than the present one. Vegetation of modern islands consists of broadleaved and sparse broadleaved forests which appeared under the impact of the anthropogenic factor. It is also noted that the areas occupied with meadow and shrubby communities are spreading. The comparative analysis of the islands by the similarity of the stages of paleovegetation development allows identifying regularities and factors of the development of vegetation cover.

An estimation of formation of soil invertebrate complexes was carried out on a common-garden provenance test with the major Siberian woody species: arolla pine (Pinus sibirica), Scots pine (Pinus silvestris), Siberian larch (Larix sibirica), Norway spruce (Picea abies, =Picea obovata), birch (Betula fruticosa), and aspen (Populus tremula). The experiment was established on a former agricultural field, so the formation of soil communities over the 30 year period combined the effects of both the reestablishment of forest conditions for soil formation and the influence of each tree species.

We evaluated parameters (stock and flux rates) carbon, nitrogen and ash element (Ca, Mg, Si, Al, Fe, P, and Mn) cycling in the plant-soil system. The study was performed in arolla pine (Pinus sibirica), Scots pine (Pinus sylvestris), Siberian larch (Larix sibirica), Norway spruce (Picea abies (=Pinus obovata)), aspen (Populus tremula) and birch (Betula fruticosa) plantations established on Kemchug upland (56°13′N, 92°19′E), Chulym-Yenisei denudational plain, in 1968–1972.